Dynamic Analysis major analyzer version bump for 18.0

Why are we doing this work

The major version for devopsapplication security testing analyzer images is bumped at least once a year, in tandem with the GitLab major release.

This issue is to bump DA analyzers to these versions:

• DAST:6
• DAST API: 6
• Fuzz API: 6

Relevant links

• Secure analyzers major version update for 18.0 (#513417 - closed) • Thiago Figueiró • 17.9

Non-functional requirements

• Documentation:
• Feature flag:
• Performance:
• Testing:

Implementation plan

Verification steps